DE3826707A1 - METHOD FOR PRODUCING AN EXHAUST MUFFLER - Google Patents

Abstract

In a process for the manufacture of an exhaust silencer for motor vehicles, the advantages derived from employing mineral fiber mouldings are extensively retained while at the same time greatly reducing expenditure on shape-stabilization and transportation. To this end the silencer casing itself is divided in the meridian plane and the mineral wool is supplied and inserted directly into the original silencer casing in the form of precisely dimensioned prefabricated elements which have been impregnated with a suitable fluid, for example pretreated with synthetic resin, but not cured. This enables fast and reliable positioning of the impregnated and manually compressed prefabricated elements around the periphery of the exhaust pipe and the internal component containing the exhaust pipe inside the original silencer casing; once the silencer casing has been closed, the silencer is ready for installation. Curing, hardening or some other time consuming method of shape-stabilization is not necessary. Nevertheless, in comparison with packing the silencer casing with loose mineral wool, a more even fiber distribution is achieved, and the introduction of a specified quantity of fibers is assured through the employment of prefabricated elements, whereby the impregnation of the prefabricated elements renders them soft and pliable and thus easy to work with when placing them in position under compression.

Description

The invention relates to a method for manufacturing an exhaust muffler according to the preamble of Claim 1.

For silencing exhaust systems from Kraft vehicles will have the exhaust pipe on a section of it Perforations on circumference, through which through vibrational energy of the exhaust gases in the Exhaust pipe surrounding space can leak. This room is closed with a along the length of the perforation surround his silencer housing, in which a filling is made of mineral wool, the sound absorption effect the vibration emerging from the exhaust pipe energy destroyed.

An obvious process for introducing the Mineral wool filling in the silencer housing consists of loose mineral wool between the exhaust pipe and plug the silencer housing and that Then finally close the silencer housing. The disadvantage here, however, is that the plugging of the loose mineral wool on the part of the silencer manufacturer leads to a not inconsiderable amount of work that negatively affects the timing of production; in such bulk products for bulk customers, namely the automotive industry, such work and time fall intensive manufacturing steps heavily weighted. Wei Thereby, the introduction of the desired Target amount of mineral wool and a sufficient equal moderate distribution of density not reliable and  regardless of the skill of the fitter targetable.

Therefore, one has gone over to the mineral wool Pages of the mineral wool manufacturer already in the for to bring the filling required shape and so to the Muffler manufacturer to deliver, then this Shaped parts only in the silencer housing are put.

To stabilize the shape of such mineral wool parts different procedures are known, such as a Wrapping loose mineral wool with a thin film and / or quilting. A common way be is also in the mineral wool on the side of the Her to provide with binder and this out harden to achieve shape stabilization.

As is practically stated on a large scale, this will used a resin-bound plate as a blank, from which the desired moldings are milled out. Here you get very dimensionally stable molded parts that Sides of the silencer manufacturer to the lowest possible Disrupt the production process. Another The advantage of this method is that the process for the production including the hardening of the plat Mineral wool on an industrial scale in the usual way can be carried out without any additional effort, and while curing the to stabilize the shape of the Sheets of binder used in the tunnel kiln of the Pro production band, so that as an additional expense after the übli Chen plate production only the milling process occurs. A However, the disadvantage of this procedure is that not inconsiderable amount of waste during the milling process occurs, which does occur again by melting again can be used, but more expensive on the  Manufacturing process of molded parts affects.

Furthermore, it is known from DE-OS 32 05 186, the Mi provided with not yet hardened binder correspond to one of the shape of the exhaust pipe arrange the core around and in one of the interior Contour of the silencer housing corresponding shapes enclose housing and harden in this position After opening the mold housing and removing it pulling the core is then a one-piece molding in the form of the desired silencer filling, which is supplied to the silencer manufacturer and by this for installation in the silencer on the actual Liche exhaust pipe can be plugged on. A disadvantage this procedure is that for the introduction the mineral wool in the form and demoulding cher workload and for curing insofar as considerable additional expenditure arises as not on the hardening integrated in the production process can be used in the tunnel furnace as it is for the production of felts or sheets for standard products is common. Hardening in a special form therefore requires special investments and additional Energy expenditure and can on the part of mineral wool manufacturer also hinder the production process.

In addition, this procedure is only possible if that Exhaust pipe and thus also the shape of the exhaust gas tube corresponding core in the form of a simple cylin ders so that the molded part after its curing device can be easily removed or attached. In the case of curved, branched or otherwise irregular shaped exhaust pipes in the area of the silencer this procedure is not applicable. For this it is from the DE-PS 32 38 638, of which the invention in the preamble of claim 1, known from the exhaust pipe  and corresponding additional elements such as partitions or the like existing original installation part of the Silencer on the part of the mineral wool manufacturer with pre-resin upholstery, but not yet finished to cover hardened mineral wool and thus into a mold bring in and harden. The mineral wool can also be slightly thicker on the mounting part will be worn as they are under the pressure of subsequently mold housing to be applied before curing yields. After curing, the built-in part becomes and the hardened mineral wool composite formed component removed from the mold housing and so to the The silencer manufacturer supplied this composite component in an extremely simple way through insertion into the actual silencer can have the housing assembled.

This procedure is even more complex and includes in one the following manufacturing steps:

• 1. Delivery of the finished installation parts for the Muffler from the muffler manufacturer to Mineral wool manufacturers,
• 2. Production of mineral wool webs with enrichment with a synthetic resin binder,
• 3. Generation of a variety of pads e.g. by Tear off or cut off the mineral wool bah no,
• 4. Insert the upholstery and the original installation part in a mold housing,
• 5. Harden the binder in a heated pre direction,  
• 6. shaping the finished composite components,
• 7. Return delivery of the built-in parts and the out hardened mineral wool existing composite components from the mineral wool manufacturer to the silencer actuator.

As can be easily seen, this is the for the production of so-called wound molded parts according to DE-OS 32 05 186 already required che effort increased by the fact that the introduction a large number of individual small cushions work is more than wrapping a straight tube with a longer mineral wool web. Furthermore falls in particular considerable additional transport effort, because each of the original installation part first from the silencer transported to the mineral wool manufacturer and after the formation of the composite component of this again who is transported back to the silencer manufacturer that must.

In contrast, the invention is based on the object a method of the generic state of the Technology known genus to create, which not only if necessary, a reduction in transport costs possible, but also without the use of complex Measures for shape stabilization, especially without before previous curing is feasible.

This problem is solved by the character nenden features of claim 1.

The invention is based on the knowledge that, for example, pre-resinated or otherwise suitably impregnated pads made of mineral wool have good internal fiber cohesion, but are nevertheless soft and shapeable and largely retain the compressed form when compressed, so they spring back only slowly and incompletely. This makes it possible to plastically deform such overlays by hand and thereby compress them - essentially remaining for a short period of time. In this way, a support delivered with the usual bulk density in the order of magnitude of, for example, 50 kg / m ³ and not brought to a substantially increased bulk density as part of an immediately preceding pretreatment, can be processed to a much higher bulk density of, for example, 150 kg / m ³ be compacted by hand; after removal of the pressure force there is still enough time before springback occurs too strongly to mount the support in a partially compressed, relatively small volume state in the silencer and to close the silencer housing without excess mineral wool volume on the contact surfaces metallic sound damper components is trapped. The invention is based on the further knowledge that working with such resin-coated pads - unlike when bringing loose mineral wool - does not lead to major delays in the silencer assembly itself and does not make any special demands on the care and skill of the assembly staff when the pads are pre-assembled in accordance with the installation conditions of the silencer to be manufactured in a precise manner typical for the respective installation site. Then it is possible to use constructions parts thus formed instead of dimensionally stabilized parts directly in the silencer assembly, without fear of adverse effects on the workflow there, especially since due to the precise confectioning, use of the confection parts with the largest possible dimensions is possible, which moreover the reproducible achievement of the target quantity to be introduced and the desired density distribution guaranteed.

Therefore, the invention proposes such impregnated, e.g. pre-resinated pads pre-assembled as confectionery tion parts, for example in the form of blanks, Stamped parts or the like instead of dimensionally stabilized Deliver molded parts to the installation location of the silencer and install it in the silencer itself. The Using a sound split in the meridian plane damper housing enables easy positionally accurate loading laying the installation part of the silencer with the front made upholstery. Then the silencer housing in the meridian plane - similar to the For set housing in the generic state of the art - closed. This excludes the use of large areas Ready-made parts instead of a variety more or we less random upholstery protruding Mineral wool parts between tightly fitting one another Metal surfaces of the muffler housing and installation partly out. Hardening does not need at all take place because a shape stabilization one without an outside Housing molded part not to be transported is such. Furthermore needs for the impregnation Ready-made parts, which makes them soft and pliable, a binder is not necessarily used, but can use any other suitable liquid impregnation be used because after installation in the Muffler the binder essentially without Function is and when starting the motor vehicle burns away in a short time. It can be impregnated selected from other points of view be, for example, the environmental impact when operating the Motor vehicle, good and inexpensive availability, good and pleasant workability, etc.  

When mounting the muffler on the muffler manufacturer takes place, so only need the imprint nated parts are transported to it, what even compared to a transport of formstabili molded parts alone to a reduction of transportation costs. Alternatively, if necessary but also the silencer assembly for mineral wool Manufacturers are made to operate the silencer to relieve the manufacturer of this effort; there then compared to the procedure according to DE-OS 32 38 638 for Installation part or in addition to the composite component Original housing of the silencer is transported, the transportation costs are therefore negligible increased, but does not require any assembly effort sides of the silencer manufacturer, who only the metal parts made by him on the mineral wool manufacturer supplies and the finished silencer received back. The transportation effort can, as far as the time This allows the coordination of the supply be reduced overall that the mineral wool set the muffler fully assembled in this way immediately to the customer of the silencer manufacturer, so the automobile manufacturer, and so does the transport from silencer manufacturer to automobile manufacturer not applicable; this is therefore possible within the scope of the invention Lich because after closing the muffler housing following the introduction of the impregnated mine wool cushions no longer work on the silencer required are.

Especially with silencer housings with elliptical or similar cross section results from the dimension took the claim 2 in a simple way a min change in density differences.

If the customer is between the mineral wool and the  A layer of metal wool on the outside of the exhaust pipe wishes to improve the blow-out behavior, so can NEN according to claim 3, the metal wool either in the form a metal fiber stocking in the course of assembly before Assignment with assembly part on a straight exhaust pipe postponed or otherwise, e.g. by point soldering to the fixture can be secured in place, or ge according to claim 4 on the installation part in the installation position facing side of the parts to be attached. According to claim 5, this attachment mechanically approximately done by quilting, or by means of an adhesive, which, however, does not become a leg for its hardening leading to impregnation of the mineral wool leading Exposure to heat required.

If necessary, a metal fiber layer to the confection Mineral wool part for sufficient attachment tion can only be pressed on by claw and Adhesion effects a sufficient position securing for the Handling of the composite parts thus formed in the Mon to achieve days.

A variety of are suitable as impregnation agents Liquids as well as the usual synthetic resin binder for such mineral wool. According to claim 6 is one Water-oil emulsion preferred, which additionally a ver improved fiber-fiber adhesion of the mineral wool and thus a stabilization of the outline shape of the finished part results. Such an emulsion is, for example, from the DE-OS 36 16 454 known, on account of further individual in this respect. While the water residue-free in the operation of the motor vehicle and without any environmental pollution evaporates, is the environment load due to the oil component is extremely low. Next good and inexpensive availability has one Emulsion also has the advantage of pleasant handling  the assembly parts during assembly.

Further details, features and advantages of the Erfin dung result from the following description an embodiment with reference to the drawing.

It shows:

Fig. 1 is an exploded view of a silencer constructed with the inventive method,

Fig. 2, two conditions used in preparing this silencer in the form of accurately fabricated garment parts to together form the upper part of the Schalldämpffüllung,

Fig. 3 in a Fig. 1 similar representation shows a cross section through a silencer in an intermediate position in the course of its manufacture, and

Fig. 4 in a representation corresponding to Fig. 3 shows a cross section through a finished, with which he inventive method manufactured silencer.

As can be seen from Fig. 1, there is a fiction silencer according to the invention to be produced from a Ge housing 1 with an upper housing half 1 a and a lower housing half 1 b and an installation part 2 and a housing 1 arranged between the installation part 2 and the silencer Filling 3 made of mineral wool, in the example in the form of 4 parts 3 a , 3 b , 3 c and 3 d .

The installation part 2 has a front connection piece 4 and a rear connection piece 5 for connection to the exhaust pipe, which is no longer shown, for example in the exhaust system of a motor vehicle. Between the connecting piece 4 and 5 , the mounting part 2 has a perforations 6 provided with pipe section 7 . The pipe section 7 made of metal is made in the example from two halves which are connected to each other at a flange 8 lying in the meridian plane. In a central part between the connecting pieces 4 and 5 , a radially arranged spacer 9 is arranged on the circumference of the pipe section 7 with a radially outer circumferential support web 10 , the contour of which speaks ent the inner contour of its contact area in the silencer housing 1 .

To the housing halves 1 a and 1 b of the Schalldämpfergehäu ses 1 passage openings 11 are provided and 12 for the connecting piece 4 and 5 of the fitting. 2 With regard to the division of the muffler housing 1 in a meridian plane 13 illustrated in FIG. 4, in which the flange 8 of the installation part 2 also lies, the through openings 11 and 12 are arranged as half nozzles on the housing half 11 a and the housing half 11 b , respectively 11 a , 12 a and 11 b , 12 b are formed, which include the connecting piece 4 and 5 on both sides when the silencer housing 1 is closed. In this position, the support web 10 lies free of play against a corresponding contact surface of the muffler housing 1 and thus ensures the desired position of the fitting 2 in the sound damper housing. 1

During operation of the exhaust silencer, pulsating exhaust gas with high vibration energy flows through the pipe section 7 . Through the perforations 6 through a pressure reduction of the vibration energy in the surrounding filling 3 made of mineral wool can take place, which destroys a large part of the vibration energy due to their sound absorption. In this way, the noise attenuation of the exhaust silencer comes about.

Since the exhaust gas has high temperature and high vibration energy, there may be a reduction in the cohesion of the mineral fibers in the filling 3 with a longer operating time, with the result that individual mineral fibers detach from the dressing, penetrate the perforation 6 and with the exhaust gas flow can be blown out in the pipe section 7 . To protect the mineral fibers of the filling 3 in the sense of an improvement in the blow-out behavior, an additional layer 14 made of metal wool can be introduced between the outer circumference of the pipe section 7 in the area of the perforations 6 and the inner circumference of the filling 3 , which layer contains the mineral wool before the immediate application protects by the hot exhaust gas.

It is common and proven practice to provide the muffler manufacturer with the filling 3 in the form of molded parts, as are illustrated, for example, in FIG. 1 , the assembly parts 3 a , 3 b , 3 c and 3 d in such a way Case would be kept in the illustrated form by a conventional, hardened binder for such purposes. The production of such molded parts takes place either in the form of a material-giving treatment of a corresponding hardened mineral fiber board to achieve the desired shape (milled parts) or by curing the mineral wool containing binder in a mold under the action of heat. As can be easily seen, such shaped parts can be used on the part of the muffler manufacturer as dimensionally stable construction parts and simply inserted together with the mounting part 2 into the muffler housing 1 and this can then be closed without any problems arising. An alternative procedure is to cover the original built-in part 2 with binder-containing, but uncured cushions and insert it into a mold housing according to the contour of the muffler housing 1 and harden it there, and the composite component thus formed after delivery to the muffler manufacturer as a whole Insert silencer housing.

As explained in the introduction, all of these have before certain disadvantages, especially what the Manufacturing and transport expenses concerns. In the event of the use of so-called milled parts is disadvantageous the additional effort for milling as well as the falling waste; in case of use in the form cured molded parts, whether manufactured individually or after assignment of the built-in part with the corresponding pole stern, is disadvantageous especially the effort for one special curing process, being in the case of delivery a built-in part with the hardened filling les still the considerable transport effort for the way and transport of the original installation parts.

From the mineral wool manufacturer's point of view, the easiest would of course be the delivery of loose mineral wool or mineral wool felt, from which suitable pieces can be torn off or cut off and stuffed into a muffler housing that is closed on the circumference, but the muffler manufacturer cannot produce a filling that meets the quality requirements with reasonable effort will. It should be noted in particular that the bulk density of a mineral wool lefilzen delivered without substantial pre-compression should be increased considerably in the order of 50 kg / m ³ by compression to, for example, 150 kg / m ³ and more, so that the mineral wool performs its intended functions in the silencer can meet as best as possible. Such a strong compression when installing the silencer is an insurmountable practical difficulty, if it is also taken into account that the target quantity of mineral wool and its density distribution must correspond to specified requirements. It must be ensured that the half-piece 11 a and 11 b or 12 a and 12 b must lie close to the outer circumference of the connecting piece 4 and 5 , the support web 10 must lie cleanly on the inner circumference of the metallic silencer housing 1 and in the Me ridianebene located 13, 15 and 16 designated peripheral flanges of the housing halves 1 a and 1 b of the sound damper housing 1 close to each other must be present so that must be no mineral wool in all these points.

In the method according to the invention, instead of molded parts with impregnated, in particular binder-containing, but not yet hardened ready-made parts 3 a , 3 b , 3 c and 3 d are worked, which are pre-assembled depending on the installation conditions in the silencer. The prefabricated elements 3 c and 3 d to form the lower in Fig. 1 parts of the filling 3 are shown in FIG. 2 in a plan view. In the example, they are punched out of a mineral wool sheet with a thickness of 50 mm in an exact shape and have an indentations 17 , 18 for the area of the connecting pieces 4 and 5 . As can also be seen in the illustration from FIG. 1, the precisely dimensioned indentations 17 and 18 result in a reduced amount of material in this area and thus, despite the uniform height of the ready-made parts 3 a , 3 b , 3 c and 3 d, a ver reduced material thickness of the filling in this area without crushing. The exact contour of the assembly parts 3 a , 3 b , 3 c and 3 d can best be determined by experiment; in any case, it is ensured that a contour resulting in a suitable deformation is available and that the compression always reproducibly executes the same shape changes.

In this way, only the impregnated but non-hardened ready-made parts 3 a , 3 b , 3 c and 3 d can be supplied to the silencer manufacturer while minimizing transport costs. The silencer manufacturer can handle the ready-made parts in a similarly simple manner to molded parts and immediately bring them into the silencer housing can, without the effort of curing the molded parts or a milling process at the mineral wool manufacturer. It is essential that the, for example, impregnated with binder, but uncured parts 3 a , 3 b , 3 c and 3 d differ in their consistency very significantly from loose, non-binder-containing or non-impregnated mineral wool; because the impregnation results in an increased suppleness and an improved cohesion of the fibers, so that the ready-made parts can be deformed plastically and, if not too strongly deformed, tend only very slowly in the sense of springback to return to their original shape. In the case of moderate compression of such a part by hand, for example, the compressed form is initially retained after the pressure has been removed and is only partially reset very slowly in the sense of springing open again. On the other hand, the cohesion of the fibers is so good that a fraying or the like of the edges designated 19 of the prefabricated elements also in the course of its plastic deformation Ver does not occur, but is maintained as a smooth surface.

The process of mounting the silencer is illustrated in more detail in FIG. 3.

As can be seen from it, the lower in Fig. 1 parts 3 c and 3 d in the lower Ge housing half 1 b of the silencer housing 1 are inserted, they are not or only slightly compressed by hand when inserting. Then the built-in part 2 is inserted into the lower housing half 1 in such a way that the spacer 9 with the supporting web 10 projects into a gap between the finished parts 3 c and 3 d , and the built-in part 2 or the pipe section 7 into the lower finished parts 3 c and 3 d indented, as can be seen from Fig. 3. As can be easily seen, the impression of the built-in part 2 has the consequence that the lateral edges 19 of the assembly parts 3 c and 3 d due to the improved by the impregnation to the fibers of the mineral wool together inward towards the pipe section 7 and thus tilt get at a distance from the peripheral flange 16 . The good cohesion of the fibers also at the front edges 19 ensures that there are no tufts or fringes in the direction of the metallic structural parts beyond a designated location and could interfere with the ge mutual system there.

Then the upper parts 3 a and 3 b are placed on the embedded in the parts 3 c and 3 d A component 2 and primed by hand vorkom. After placing the upper casing half 1a, the two housing halves 1 A and 1 b to form the finished silencer housing 1 as shown in Fig. 4 is shown, are pressed together, the filling 3 of mineral wool, without disturbing to the metallic contact surfaces, in the final desired shape is pressed. The assembly parts 3 a , 3 b , 3 c and 3 d predominantly with their side edges 19 in the plane To stand against each other in the meridian plane 13 , so that in the example of an elliptical muffler housing 1 on both sides of the pipe section 7 a large Amount of mineral wool is present and fills the enlarged space there with sufficient density.

In the present example, as can be seen in particular from FIG. 4, the width of the assembly parts 3 a , 3 b , 3 c and 3 d is essentially chosen according to the length of the wall of the respective housing half 1 a or 1 b at the installation site been, so that, as also Fig. 3 illustrates, nestling of the respective assembly parts to the curvature of the associated half housings laterally inward edges 19 which end in the area of the meridian plane 13 and transfer into the bottom surface of the assembly part. However, can also be achieved in other designs of a muffler by skillful choice of the arrangement and contour of the Kon fection parts and corresponding additional experiments that the mineral wool of the confection parts is deformed during compression in such a way that a good filling of all sound Technically significant gaps results and density differences in the mineral wool in the finished silencer are limited.

If, as indicated in Fig. 4, a final flanging of the edges of the housing halves 1 a and 1 b in the region of the peripheral flanges 15 and 16 takes place in the usual manner, the silencer is hermetically sealed and hen with a proper filling verse hen. The special work step of curing the filling, if binder is used as the impregnating agent, can be completely omitted, since in this position an additional shape stabilization of the mineral wool is no longer necessary. In the case of the use of binders as impregnating agents, however, curing will still take place under the influence of the hot combustion gases when the motor vehicle is started up, which is harmless in any case, but may also be advantageous with a view to improving the blow-out behavior, since the position of the individual fibers in the position reached additionally secures.

As is readily apparent from the above description, layers 14 of metal wool, in particular in tubular form, can be attached to the mounting part before the filling 3 is applied, for example pushed up or soldered on. However, it is alternatively also possible to attach a corresponding layer 14 of metal wool or the like to the ready-made parts 3 a , 3 b , 3 c and 3 d in advance, for example by quilting or gluing, or simply by adhesion as a result of mutual fiber clawing. As a result, the deformation behavior of the highly deforming, the built-in part 2 adjacent sides of the assembly parts 3 a , 3 b , 3 c and 3 d is changed to a certain extent, which if necessary can be used for a targeted local reduction in the deformability.

Resin binder, as is usually the case for Hardening of mineral fiber molded parts or sheets has been found to be with respect to the deformation behavior and handling particularly advantageous proven. However, since the binder hardens from is of minor importance, can bring about the desired consistency and the desired ver holding the ready-made parts also a different imprint  Nierungsmittel be used, such as a Water-oil emulsion or the like.

Claims (6)

1.Method for producing a muffler with a passage part ( 2 ) serving for the passage of an exhaust gas flow, and a filling ( 3 ) of mineral wool arranged in the cavities between the installation part ( 2 ) and the muffler housing ( 1 ), in which the Installation part ( 2 ) covered with mineral wool felt provided with an impregnating agent, and this arrangement with a shape corresponding to the interior of the silencer housing ( 1 ), characterized in that

• - That one in its meridian level in two housing halves ( 1 a , 1 b ) and at the division level permanently closable silencer housing ( 1 ) is used,
• - That the cushions are pre-assembled according to their respective position in the silencer
• - That the assembly parts thus formed ( 3 a , 3 b , 3 c , 3 d ) at the installation site of the muffler together with the built-in part ( 2 ) in the open muffler housing ( 1 ) even under compression and this is then permanently closed, and
• - That the muffler provided with the impregnated assembly parts is used without prior heat treatment of the assembly parts for installation in the exhaust pipe.

2. The method according to claim 1, characterized in that the assembly parts ( 3 a , 3 b , 3 c , 3 d ) are pre-assembled in a width which is the arc length of the inner wall of the associated housing half ( 1 a or 1 b ) between them lateral edges at the installation point corresponds at least approximately. 3. The method according to claim 1 or 2, characterized in that the built-in part ( 2 ) is covered before with the ready-made parts at perforated areas with a metal fiber layer ( 14 ). 4. The method according to claim 1 or 2, characterized in that a layer ( 14 ) made of metal fibers is attached to the part ( 2 ) facing the assembly parts in the installation position before installation. 5. The method according to claim 4, characterized in that for fastening the layer ( 14 ) of mineral wool and metal fibers mechanical means such as steppes or the like are used or an adhesive is used ver. 6. The method according to any one of claims 1 to 5, characterized ge indicates that a Water-oil elmusion is used.